Method of increasing octane number of motor fuel



Patented Apr. 1, 1947 METHOD OF INCREASJNGOCTANE NUMBER7 OF MOTOR FUEL George W. Ayers, Chicago, Ill., assignor to The Pure Oil Company, Chicago, 111., a corporation No Drawing. Application. June $erial N0. 598,925

- 9 Claims. (C1. 260-6835) This invention relates to a method for increasing the octane value of gasoline and of hydrocarbons boiling within'the gasoline range.

It is well-known that straight-chain parafifin hydrocarbons having 5 or more carbon atoms in the molecule have low anti-knock value and for that reason are objectionable in gasoline used for ignition type internal combustion engines. Various methods have been proposed for converting straight-chain parafilns to other types ofliydro ably placed above the bottom of the vessel in order to prevent any water which settles out of the gasoline from coming in contact with the cyanide and dissolving it; The cyanide is insoluble in carbons which have higher anti-knock value. One

such method is to isomerize these hydrocarbons to branched-chain hydrocarbons using aluminum chloride and other isomerizin catalysts.

the gasoline and can be usedindefinitely.

Although the gasoline may be mixed or agitated in order to bring it into more intimate contact with cyanide and thereby reduce the time of contact, agitation is not necessary. The treatment is carried out at ordinary atmospheric temperatures andpressures and the efiectiveness of these metal cyanides in increasing octane num- The" diflicult'y with the Friedel Crafts and other isomerizing catalysts which are known for isomerizing straight-chain paraifins to iso-paraffins is that these catalysts are reactive with respect to unsaturated and aromatic hydrocarbons, causing loss of these constituents in the motor fuel. Furv thermore, Friedel-Crafts type catalysts cause" some cracking of the liquid hydrocarbons to gaseous hydrocarbons. N

I have discovered that if straight-chain hydrocarbons or gasoline containing straight-chain laydrocarbons is allowed to stand in contact with certain metal cyanides fora sufliciently long period of time, isomerization of the straight-chain hydrocarbons to hydrocarbons having high octane value occurs, so that-the overall octanenumber of the hydrocarbon or hydrocarbon mixture is higher than the material before treatment with the cyanide. The metal cyanides which are effective for improving the octane number of straight-chain paraffin hydrocarbons are potassium cyanide, cuprous cyanide, nickel cyanide, mercuric cyanide and silver cyanide. The aforesaid metal cyanides are efiective in improving octane number of liquid hydrocarbon mixtures containing straight-chain paraflin hydrocarbons in the presence of unsaturated and aromatic hydrocarbons without afiecting the latter, so that no loss in the gasoline boiling constituents occurs.

The treatment of the gasoline or gasoline-boiling hydrocarbons .With the metal cyanide may be efiected simply by permitting the gasoline to stand in contact with powdered, granular or lump cyanide for a period of time in excess of two days and preferably for a period of more than twenty days. A simple method for effecting contact is to place granular metal cyanide in liquid permeable containers in a vessel in which the gasoline is stored, or to place lump metal cyanide on one or more perforated trays in the vessel containing the gasoline. The cyanide is prefer ber doesnot appear to be affected by temperature or pressure. The treatment can be carried out at temperatures as low as -4() F. and as high as 500 F.

' The amount of cyanide which is contacted with the gasoline .or other hydrocarbon material may range from atrace to as much as 100% by weight or more of the gasoline.

The following examples will demonstrate the efiectiveness of the metal cyanides in improving the octane number of gasoline or gasoline-boiling hydrocarbons:- a

. Example I 600. cc. of gasoline comprising :a blend-of straight-run and high pressure, thermally cracked Emample II 600 cc. of the same gasoline used in Example I was allowed to stand in a closed vessel for thirtythree days with grams of granular cuprous cyanide. No noticeable change in the cuprous cyanide occurred. The gasoline before treatment had an A. S. T. M. octane number of 59.6 and after the treatment had an octane number of 60.2.

I Example III 500 cc. of nheptane was allowed to stand in a closed vessel for thirty-three days with 20 grams of granular potassium cyanide. The potassium cyanide remained unchanged, but the A. S. T, M. octane number of the n-heptane was 2.3 after r it was found to contain 4% of iso-paraflins.

the treatment as compared to an A. S. T. M. octane number of zero before treatment.

Example IV cuprous cyanide occurred, but the n-heptane hadan A. S. T. M. octane number of 2 after the treatment as compared to an A. S. T. M. octane number of zero before the treatment.

Example V 25 cc. of n-heptane was allowed to I stand at room temperature in a closed vessel for fOrty two days in contact with 3 cc. of a saturated aqueous potassium cyanide solution. At the end of this time the hydrocarbon material was analyzed by the modified Moldavskii method, described and claimed, in'application, Serial No. 474,748. and It will be seen, therefore, that the solution of the cyanide was also effective in causing isomerization.

The modified Moldavskii method difiers from the conventional Moldavskii method, principally in that approximately 0.05 gram of dry uranyl nitrate isadded to each 25 cc. of solution in connection with chlorination with antimony pentachloride and the solution is allowed to stand for at least six hours in a closed vessel at a temperature of 70-90 F. in order to complete the chlorination.

Although the increase in octane number is not large, it is significant and is obtained at substantially no expense other than the initial cost of the cyanide which may be used over and over again to treat new batches of gasoline. The treatment is applicable to gasoline either before or after the addition of tetraethyl lead and can be carried out at the refinery or during storage at any other point such as a bulk plant or service station.

It wille be seen, therefore, that I have found a simple and inexpensive method for improving the knock reading of motor fuels without causing any loss of the motor fuel.

4 It is claimed: 1. The method of improving the anti-knock value of gasoline-boiling parafilnic hydrocarbons when used in ignition-type internal combustion engines comprising contacting said hydrocarbons for a period of at least two days with a metal cyanide insoluble in said hydrocarbons selected from the group consisting of potassium cyanide, cuprous cyanide, nickel cyanide, mercuric cyanide and silver cyanide and separating said hydrocarbons from the cyanide.

2. Method in accordance with claim 1 in which the cyanide is potassium cyanide.

3. Method in accordance with claim 1 in'which the cyanide is cuprous cyanide.

4. Method in accordance with claim 1 in which the cyanide is nickel cyanide.

5. The method of improving the anti-knock value of gasoline-boiling hydrocarbons contain.- ing a substantial amount of straight chain par- 'a'filnic hydrocarbons when used in ignition-type internal combustion engines comprising contacting said hydrocarbons under existing atmospheric conditions with a metal cyanide insoluble in said hydrocarbons selected from the group consisting of potassium cyanide, cuprous cyanide, nickel cyanide, mercuric cyanide, and silver cyanide for a period of time not less than two days sufficient to effect an increase in octane number and separating the hydrocarbons from the cyanide.

'6. Method in accordance with claim 5 in which theperiod of time is at least twenty days.

7. Method in accordance Withclaim 5 in which the metal cyanide is potassium cyanide.

8. Method in accordance with claim 5 in which the metal cyanide is cuprous cyanide.

9. Method in accordance with claim 5 in which the metal cyanide is nickel cyanide.

GEORGE W. AYERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Rosenstein Sept. 25, 1934 

